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Science in international negotiations

The Climate Change Convention: a load of hot air?

By Peter Hulm

The IPCC consensus on climate change

The Intergovernmental Panel on Climate Change (IPCC) said that many climatologists believe that global warming as a result of the accumulation of trace gases in the atmosphere could raise the world's average temperature by 2°C within 50 years and mean sea-levels would rise by around 30-50cm by 2030 (McNeely, 1995, p 27, citing Warrick, 1988).

McNeely (1995:27) summarizes the degrees of consensus found by the panel as follows:

Issue

Statement

Consensus

Basic characteristics

Fundamental physics of the greenhouse effect

Virtually certain

 

Added greenhouse gases add heat

Virtually certain

 

Greenhouse gases increasing because of human activity

Virtually certain

 

Significant reduction of uncertainty will require a decade or more

Virtually certain

 

Full recovery will require many centuries

Virtually certain

Projected effects by mid-21st Century

   
 

Large stratospheric cooling

Virtually certain

 

Global mean surface-precipitation increase

Very probable

 

Reduction of sea ice

Very probable

 

Arctic winter surface warming

Very probable

 

Rise in global sea-level

Uncertain

 

Local details of climate change

Uncertain

 

Tropical storm increases

Uncertain

 

Details of next 25 years

Uncertain

In this table,

Virtually certain means there is nearly unanimous agreement among scientists and no credible alternative view

Very probable means there is roughly a 90% chance of occurrence

Probable means there is approximately a 2/3 chance of occurrence

Uncertain means the evidence is lacking for the hypothesized effect

References

Summary

Introduction

The scientific consensus

The problems of consensus

The politics of consensus

The threshold of danger

The politics of science

Knowledge-based communities

'Greenwash'

Buying scientific credibility

Science and the three paradigms

A utilitarian hypothesis

A cobweb model, modified

Conclusion


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11 December 2000 Webmaster